This invention relates to an air separation plant integrated with another process. Work is recovered from the nitrogen enriched stream produced by the air separation either by expanding the nitrogen enriched stream directly or by combustion of the nitrogen enriched stream with a fuel stream and expanding gas produced by the combustion. The present invention is related to an integrated power generation system process and apparatus in which a nitrogen enriched stream from an air separation unit is sent to a point upstream of the expander of a gas turbine.
Such integrated systems are well known. For example, EP-A-0622535 discloses an integrated power generation system in which nitrogen from an air separation unit is mixed with air and the mixture is sent to the compressor of a gas turbine and subsequently to the combustor. The nitrogen is cooled by expansion or addition of water before the mixing step to increase the gas throughput in the compressor.
EP-A-0538118 describes mixing nitrogen and compressed air from the air compressor before sending the mixture to the combustor of a gas turbine.
In U.S. Pat. No. 5,076,837, a nitrogen stream is heated using a waste gas stream before being expanded in a turbine. The waste gas stream is produced by a chemical process using oxygen from the air separation unit.
EP-A-0225864 uses combustion gases to preheat nitrogen from an adsorption process before expanding the nitrogen in a turbine.
U.S. Pat. No. 4,785,621 discloses an air compressor which produces two air streams, one of which is sent to an air separation unit. The other air stream is mixed with the nitrogen produced by the air separation, warmed using waste heat from a fired gas turbine and subsequently expanded in a turbine.
JP-A-57183529 and JP-A-57083636 describe a coal gasification power plant in which nitrogen from an air separation unit is mixed with air, compressed and sent to a combustor to produce combustion gas.
In U.S. Pat. No. 3,731,495 air from a gas turbine compressor is divided in three. One part feeds an air separation unit producing impure nitrogen, one part is sent to the combustor and the rest is mixed with the gases from the combustor and the impure nitrogen at a temperature of about 1350xc2x0 F.
U.S. Pat. No. 4,557,735 shows a similar arrangement in which nitrogen which has served to regenerate the adsorbent beds is sent to the combustor of a gas turbine. In this case, an air stream is mixed with the compressed nitrogen and sent to the combustor.
According to one aspect of the invention, there is provided an integrated power generation system apparatus comprising an air separation unit, a gas turbine comprising a combustor and an expander, a first compressor, means for sending air from the first compressor to the combustor and to the air separation unit, means for sending a nitrogen enriched stream from the air separation unit to a point upstream of the expander, and means for sending a further gas enriched in a component chosen from the group comprising oxygen, argon and carbon dioxide to a point upstream of the expander.